In general, flashlights have a rigid structure, which are not adjustable in length and orientation so that it is often that the flashlight is inconvenient for lighting a deep or bending section, especially, in repairing some machines with large sizes and complicated structures. Moreover, a medical treatment, such as treating the diseases with ears, throats, etc., it is necessary to insert a flashlight into the deep portion of the organ. However, the prior art flashlight is not practical in theses applications.